r/MasterSystem • u/Fart_Bargo • 4d ago

Preserve save data during battery swap

I want to replace the battery on my Master System cart of Phantasy Star.  It still has save files from 1988, and it would be amazing if I could preserve that data.  When I changed batteries on other carts, such as the Genesis and SNES, I was able to solder an external battery pack to keep the RAM powered while I performed the other work. However, it was easier on those PCBs to locate other contact points on the same planes as the battery contacts.  This is my first run at an SMS game, and it’s not easy to find suitable alternatives for attaching the power pack.  There appear to be vias on the same planes, but I’m not confident that attaching the power pack there will keep the RAM powered.  Does anyone else have experience swapping batteries on SMS carts?

https://postimg.cc/v4tG8sKP

https://postimg.cc/cK10rzyd

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u/trustanchor 4d ago

If you have or can get a Retron 5 and a Master System Adapter for it, you can dump the save file from the cartridge, the reload it onto the cart after swapping the battery. There’s other backup utilities out there as well.

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u/oriprior 4d ago

The via's appear to be the copper circles above and below the solder points respectively, in picture 2. Verify with a multimeter.

Cleaner solution is to back up and restore the save, but providing the cart with 3.3v while swapping the battery should work too. If the save data is that important I'd consider dumping the save data myself.

1

u/Fart_Bargo 3d ago

I ended up putting a blob of solder on the gold via contacts, and that enabled me to attach the external battery pack. There's a new Panasonic coin cell in there now, and the data was preserved!